This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2000-259541, filed Aug. 29, 2000, the entire contents of which are incorporated herein by reference.
The inventions described herein relate to an illumination device for a projection-type display and a projection-type display apparatus, which use efficiently a light integrator.
It is a conventional trend to use discharge lamps such as mercury lamps, metal halide lamps, or xenon lamps as light sources of projection-type displays.
However, a light source based on a lamp contains many unnecessary light components which are cut by an optical filter such as a UV filter, an IR filter, a dichroic mirror, or the like in the projection-type display generally utilizing optical driving based on three primary colors. As a result, this involves factors which do not only cause increase in costs but also cause various drawbacks due to stray light and heat generation.
Optical semiconductor elements such as LEDs and the like may be cited as new candidates for light sources which will substitute those light sources that have been described above. For example, an InGaAlP (red) LED 1 element has a forward voltage of about 2 V, by the standards, in normal use at 20 mA, and the electric power of the light source is only 0.04 W. A large number of such light sources are required for a projection-type display light source. Further, these semiconductor elements have drawbacks of a large light diffusion angle, a high refraction factor, and an inferior transmittance to the air. To overcome these drawbacks, it may be considered that a reflector should be provided in the side opposite to the side of the irradiation surface and the lamp element surface should be covered with resin material or the like having a lens-like shape, to improve the directivity and the light extraction efficiency, as can be seen in a normal single LED lamp structure.
However, in this structure, the shape of the light source has a large size in case where a large number of single LED lamps are provided, so that the system is enlarged much and the costs increase. In addition, in case of using liquid crystal for light valves, for example, the illumination angle becomes so large that the video quality including contrast and the like is lowered due to influences from the view field. Many drawbacks have hence been involved, e.g., it is very difficult to construct an optical system including a projection lens member, which achieves light condensation with high efficiency.
As described above, a conventional projection-type display has a light source having a large size. The number of parts increases, complicating the structure. Another problem exists in that the light amount is insufficient when LEDs are used.
The inventions described herein provide an illumination device for a projection-type display and a display apparatus, each of which has a simple structure and a small size and can obtain a sufficient illumination amount.
The inventions also provide an illumination device for a projection-type display, which has improved illumination ability and high reliability.
The inventions also provide an illumination device for a projection-type display with high performance at low costs.
An illumination device according to the present invention comprises: a light integrator having an irradiation surface opposed to a light valve and positioned in a side of light incidence part of the light valve such that a center axis of the irradiation surface substantially corresponds to an optical axis of the light bulb, a diffusive reflection surface arranged at an interval from the irradiation surface, and a reflection mirror surrounding a space between the irradiation surface and the diffusive reflection surface, the light integrator having a cross-sectional area larger than the diffusive reflection surface at any position in the center axis direction; and a light source having light guide means for guiding light toward the diffusive reflection surface in the light integrator.
A projection-type display apparatus according to the present invention comprises: a light valve; a light integrator having an irradiation surface opposed to the light valve and positioned in a side of light incidence part of the light valve such that a center axis of the irradiation surface substantially corresponds to an optical axis of the light valve, a diffusive reflection surface arranged at an interval from the irradiation surface, and a reflection mirror surrounding a space between the irradiation surface and the diffusive reflection surface, the light integrator having a cross-sectional area larger than the diffusive reflection surface at any position in the center axis direction; and light guide means for irradiating a laser beam toward the diffusive reflection surface in the light integrator.
A distance Ls between the diffusive reflection surface and the light emission part of the light guide means is expressed by a function using at least a as a reflection area of the diffusive reflection surface, b as an area of a light valve illumination setting range depending on the irradiation surface, d as a distance from the diffusive reflection surface to the irradiation surface, and xcex94xcex8 as an insertion angle of the light guide means at a position where the light guide means is inserted in the light integrator.
The diffusive reflection surface is formed in a convex shape having a curvature.
The diffusive reflection surface is formed in a convex shape having a curvature, and the distance Ls between the diffusive reflection surface and the light emission part of the light guide means is expressed by a function using at least a as a reflection area of the diffusive reflection surface, b as an area of a light valve illumination setting range depending on the irradiation surface, d as a distance from the diffusive reflection surface to the irradiation surface, and xcex94xcex8 as an insertion angle of the light guide means at a position where the light guide means is inserted in the light integrator.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter